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A LevelBIOLOGY

Practical Log Book

Biology apparatus and techniques

Apparatus and techniquesAT a use appropriate apparatus to record a range of quantitative measurements (to include mass,

time, volume, temperature, length and pH)

AT b use appropriate instrumentation to record quantitative measurements, such as a colorimeter or potometer

AT c use laboratory glassware apparatus for a variety of experimental techniques to include serial dilutions

AT d use of light microscope at high power and low power, including use of a graticule

AT e produce scientific drawing from observation with annotations

AT f use qualitative reagents to identify biological molecules

AT g separate biological compounds using thin layer/paper chromatography or electrophoresis

AT h safely and ethically use organisms to measure: plant or animal responses physiological functions

AT i use microbiological aseptic techniques, including the use of agar plates and broth

AT j safely use instruments for dissection of an animal organ, or plant organ

AT k use sampling techniques in fieldwork

AT l use ICT such as computer modelling, or data logger to collect data, or use software to process data

Biology required activities (1-6 AS), (1-12 A-level)

Required activity Apparatus and technique reference

Completed on: Signed

1. Investigation into the effect of a named variable on the rate of an enzyme-controlled reaction

a, b, c, f, l

2. Preparation of stained squashes of cells from plant root tips; set-up and use of an optical microscope to identify the stages of mitosis in these stained squashes and calculation of a mitotic index

d, e, f

3. Production of a dilution series of a solute to produce a calibration curve with which to identify the water potential of plant tissue

c, h, j, l

4. Investigation into the effect of a named variable on the permeability of cell-surface membranes

a, b, c, j, l

5. Dissection of animal or plant gas exchange or mass transport system or of organ within such a system

e, h, j

6. Use of aseptic techniques to investigate the effect of antimicrobial substances on microbial growth

c, i

7. Use of chromatography to investigate the pigments isolated from leaves of different plants eg leaves from shade-tolerant and shade- intolerant plants or leaves of different colours

b, c, g

8. Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts

a, b, c, l

9. Investigation into the effect of a named variable on the rate of respiration of cultures of single-celled organisms

a, b, c, h, i, l

10. Investigation into the effect of an environmental variable on the movement of an animal using either a choice chamber or a maze

h

11. Production of a dilution series of a glucose solution and use of colorimetric techniques to produce a calibration curve with which to identify the concentration of glucose in an unknown ‘urine’ sample

a, b, c, f, l

12. Investigation into the effect of a named environmental factor on the distribution of a given species

a, b, h, k, l

My Apparatus and Technique Tracker

Appa

ratu

s and

Tec

hniq

ue R

efer

ence

Description1.

Inve

stiga

tion

into

the

effec

t of a

nam

ed v

aria

ble

on th

e ra

te o

f an

enzy

me-

cont

rolle

d re

actio

n (U

NIT

1)

2. P

repa

ratio

n of

stai

ned

squa

shes

of c

ells

from

pla

nt ro

ot ti

ps; s

et-

up a

nd u

se o

f an

optic

al m

icro

scop

e to

iden

tify

the

stag

es o

f mito

sis

in th

ese

stai

ned

squa

shes

and

cal

cula

tion

of a

mito

tic in

dex

(UN

IT 2

)

3. P

rodu

ction

of a

dilu

tion

serie

s of a

solu

te to

pro

duce

a c

alib

ratio

n cu

rve

with

whi

ch to

iden

tify

the

wat

er p

oten

tial o

f pla

nt ti

ssue

(UNI

T 2) 4.

Inve

stiga

tion

into

the

effec

t of a

nam

ed v

aria

ble

on th

e pe

rmea

bilit

y of

cell-

surf

ace

mem

bran

es (U

NIT

2)

5. D

issec

tion

of a

nim

al o

r pla

nt g

as e

xcha

nge

or m

ass t

rans

port

sy

stem

or o

f org

an w

ithin

such

a sy

stem

(UNI

T 3)

6. U

se o

f ase

ptic t

echn

ique

s to

inve

stiga

te th

e eff

ect o

f anti

micr

obia

l su

bsta

nces

on

micr

obia

l gro

wth

(UN

IT 4

)

aUse appropriate apparatus to record a range of quantitative measurements (to include mass, time, volume, temperature, length and pH)

bUse appropriate instrumentation to record quantitative measurements, such as a colorimeter or potometer

cUse laboratory glassware apparatus for a variety of experimental techniques to include serial dilutions

d Use of light microscope at high power and low power, including the use of a graticule

e Produce scientific drawing from observation with annotations

f Use qualitative reagents to identify biological molecules

g Separate biological compounds using thin layer/ paper chromatography or electrophoresis

hSafely and ethically use organisms to measure (a) plant or animal responses; (b) physiological functions

i Use microbiological aseptic techniques, including the use of agar plates and broth

j Safely use instruments for dissection of an animal organ or plant organ

k Use sampling techniques in fieldwork

lUse ICT such as computer modelling, or data logger to collect data, or use software to process data

Appa

ratu

s and

Tec

hniq

ue R

efer

ence Description

7. U

se o

f chr

omat

ogra

phy

to in

vesti

gate

the

pigm

ents

isol

ated

from

le

aves

of d

iffer

ent p

lant

s, eg

leav

es fr

om sh

ade-

tole

rant

and

shad

e-in

tole

rant

pla

nts o

r lea

ves o

f diff

eren

t col

ours

(UNI

T 5)

8. In

vesti

gatio

n in

to th

e eff

ect o

f a n

amed

fact

or o

n th

e ra

te o

f de

hydr

ogen

ase

activ

ity in

ext

ract

s of c

hlor

opla

sts (

UNIT

5)

9. In

vesti

gatio

n in

to th

e eff

ect o

f a n

amed

var

iabl

e on

the

rate

of

resp

iratio

n of

cultu

res o

f sin

gle-

celle

d or

gani

sms (

UNIT

5)

10. I

nves

tigati

on in

to th

e eff

ect o

f an

envi

ronm

enta

l var

iabl

e on

the

mov

emen

t of a

n an

imal

usin

g ei

ther

a ch

oice

cham

ber o

r maz

e (U

NIT

6) 11. P

rodu

ction

of a

dilu

tion

serie

s of g

luco

se so

lutio

n an

d us

e of

co

lorim

etric

tech

niqu

es to

pro

duce

a ca

libra

tion

curv

e w

ith w

hich

to

iden

tify

the

conc

entr

ation

of g

luco

se in

an

unkn

own

'urin

e' sa

mpl

e (U

NIT

6)

12. I

nves

tigati

on in

to th

e eff

ect o

f a n

amed

env

ironm

enta

l fac

tor o

n th

e di

strib

ution

of a

giv

en sp

ecie

s (UN

IT 7

)

T1 -

T2 -

T3 -

aUse appropriate apparatus to record a range of quantitative measurements (to include mass, time, volume, temperature, length and pH)

bUse appropriate instrumentation to record quantitative measurements, such as a colorimeter or potometer

cUse laboratory glassware apparatus for a variety of experimental techniques to include serial dilutions

d Use of light microscope at high power and low power, including the use of a graticule

e Produce scientific drawing from observation with annotations

f Use qualitative reagents to identify biological molecules

g Separate biological compounds using thin layer/ paper chromatography or electrophoresis

hSafely and ethically use organisms to measure (a) plant or animal responses; (b) physiological functions

i Use microbiological aseptic techniques, including the use of agar plates and broth

j Safely use instruments for dissection of an animal organ or plant organ

k Use sampling techniques in fieldwork

lUse ICT such as computer modelling, or data logger to collect data, or use software to process data

Common Practical Assessment Criteria (CPAC) criteria for A level Biology.

Common Practical Assessment Criteria (CPAC)

The criteria for a Pass

In order to be awarded a Pass a learner must, by the end of the practical science assessment, consistently and routinely meet the criteria in respect of each competency listed below. A learner may demonstrate the competencies in any practical activity undertaken as part of that assessment throughout the course of study.

Learners may undertake practical activities in groups. However, the evidence generated by each learner must demonstrate that he or she independently meets the criteria outlined below in respect of each competency.

Such evidence:

(a) will comprise both the Learner’s performance during each practical activity and his or her contemporaneous record of the work that he or she has undertaken during that activity, and

(b) must include evidence of independent application of investigative approaches and methods to practical work.

CPAC 1:Follows written procedures

(a) Correctly follows instructions to carry out the experimental techniques or procedures.

CPAC 2:Applies investigative approaches and methods when using instruments and equipment

(a) Correctly uses appropriate instrumentation, apparatus and materials (including ICT) to carry out investigative activities, experimental techniques and procedures with minimal assistance or prompting.

(b) Carries out techniques or procedures methodically, in sequence and in combination, identifying practical issues and making adjustments when necessary.

(c) Identifies and controls significant quantitative variables where applicable, and plans approaches to take account of variables that cannot readily be controlled.

(d) Selects appropriate equipment and measurement strategies in order to ensure suitably accurate results.

CPAC 3:Safely uses a range of practical equipment and materials

(a) Identifies hazards and assesses risks associated with these hazards, making safety adjustments as necessary, when carrying out experimental techniques and procedures in the lab or field.

(b) Uses appropriate safety equipment and approaches to minimise risks with minimal prompting.

CPAC 4:Makes and records observations

(a) Makes accurate observations relevant to the experimental or investigative procedure.

(b) Obtains accurate, precise and sufficient data for experimental and investigative procedures and records this methodically using appropriate units and conventions.

CPAC 5:Researches, references and reports

(a) Uses appropriate software and/or tools to process data, carry out research and report findings.

(b) Sources of information are cited demonstrating that research has taken place, supporting planning and conclusions.

My CPAC Tracker

A-level Biology required practical No. 1

Investigation into the effect of a named variable on the rate of an enzyme-controlled reaction.

The effect of temperature on the rate of the reaction catalysed by trypsin.

Casein is a protein found in milk. Trypsin is an enzyme that digests casein. When trypsin is added to a dilute solution of milk powder, the casein is digested and the solution goes clear.

Method

You are provided with the following:

0.5% trypsin solution 3% solution of milk powder pH 7 buffer solution a large beaker to use as a water bath test tubes test-tube rack stopwatch marker pen pipettes or syringes thermometer

You are required to find the rate of reaction at five different temperatures. Your teacher will tell you whether you are going to investigate all the temperatures yourself or whether you will get some results from other students in your class.

You should read these instructions carefully before you start work.

1. Using a marker pen write an ‘X’ on the glass halfway down one side of each of three test tubes.

2. Add 10 cm3 of the solution of milk powder to each of these three test tubes.3. Add 2 cm3 of trypsin solution to 2 cm3 of pH 7 buffer in another set of three test tubes.4. Stand the three test tubes containing the solution of milk powder and the three test tubes

containing trypsin and buffer in a water bath at 20 °C.5. Leave all six tubes in the water bath for 10 minutes.6. Add the trypsin and buffer solution from one test tube to the solution of milk powder in

another test tube and mix thoroughly.7. Put the test tube back into the water bath.8. Repeat steps 6 and 7 using the other test tubes you set up.9. Time how long it takes for the milk to go clear by measuring the time taken to first see the

‘X’ through the solution.10. Record the time for each of the three experiments.

11. Using the same method, find out how long it takes the trypsin to digest the protein in the solution of milk powder at 30 °C, 40 °C, 50 °C, 60 °C.

12. Record your data in a suitable table.13. Process your data and draw a graph of your processed data.

EXT. (a) A protein is formed from 300 amino acids. The diagrams show the primary, secondary and tertiary structures of this protein.

(i) Explain what causes the secondary structure to differ in length from the primary structure.

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(ii) Explain what is meant by the tertiary structure of a protein.

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(iii) Heating may affect the tertiary structure of a protein. Explain how.

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(c) The first step in investigating the primary structure of a protein is to break it into shorter lengths with enzymes. The table shows some of the enzymes used and the position of the peptide bonds they break.

The diagram shows a polypeptide chain. The sequence of amino acids should be read from left to right.

(i) How many amino acid fragments will be produced from this polypeptide if it is incubated with a mixture of trypsin and V8 protease?

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...................(1 mark)

(ii) Explain why trypsin and chymotrypsin break peptide bonds between different amino acids.

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Preparation of stained squashes of cells from plant root tips; set up and use of and optical microscope to identify the stages of mitosis in these stained squashes and calculation of a mitotic index

Root tip squash using onion root meristem tissue


100 ml beaker hydrochloric acid (5 mol dm–3) microscope slide and cover slip toluidine blue stain filter paper mounted needle scalpel distilled water watch glass forceps root tip of onion or garlic microscope and light source

You are required to prepare a microscope slide of the meristem tissue from an onion root. You will add a stain to the material which allows you to see the chromosomes. You will look at the slide under the microscope to identify any cells showing stages of mitosis. You will then calculate the mitotic index.

Safety

Hydrochloric acid (5 mol dm–3) is corrosive and should be handled with caution. Eye protection must be worn.

The beaker must be stood on a bench mat. Do not carry the beaker with acid in it.

NB Do not leave root tips for investigation lying about on the bench top prior to staining. Cut your root tip immediately before you put it into the acid. This will stop any reactions and hopefully some cells will be in a stage of division.

Making your slide

1. Stand the beaker on a bench mat before adding approximately 10 ml of hydrochloric acid (5 mol dm–3)

2. Place about 2 cm of root tip in the acid and leave for 15 minutes.3. Set up your microscope while you are waiting.4. Rinse the root tip in distilled water in the watch glass.5. Cut off the root tip (1 mm) and place on a microscope slide.6. Cover the section with toluidine blue stain and macerate with the mounted needle to separate

the cells.7. Continue to macerate until the tissue is well broken and the cells are stained dark blue.8. Add a cover slip and with gentle finger pressure ‘spread’ the material and blot at the same

time by using a folded filter paper between finger and slide.9. Look carefully at all slides for cells undergoing mitosis. Chromosomes should stain dark blue.

Repeat for several fields of view.10. Record your data in a suitable table.11. Calculate the mitotic index.

EXT. (a) Complete the following table. Use a tick if the feature is present or a cross if it is absent.

(3 marks)

(b) Cells were scraped from the cut surface of a potato tuber. They were stained with iodine solution and examined with an optical microscope. The drawing shows one of these cells.

(i) Name two polysaccharides found in this cell which would not be found in a red blood cell.

1. .............................................................................................................................................................

2. ...............................................................................................................................................................

(1 mark)

(ii) The diameter of this cell, measured from A to B, is 40 µm.Calculate the magnification of the drawing. Show your working.

Answer ............................................

(2 marks)

(ii) The focusing knob of the microscope was adjusted slightly. The drawing below shows how the cell then looked.

Explain the difference in appearance of the cell contents.

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Production of a dilution series of a solute to produce a calibration curve with which to identify the water potential of plant tissue

Determining the water potential of potato tuber cells


large potato tuber core borer of known diameter 1 mol dm–3 sucrose solution distilled water boiling tube rack six boiling tubes, marker pen thermometer 10 cm3 graduated pipette and pipette filler white tile scalpel or small kitchen knife ruler paper towels timer digital balance forceps


Preparing the dilution series

1. Label six boiling tubes 0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol dm–3 sucrose.2. Use the 1.0 mol dm–3 sucrose solution and water to make up 20 cm3 of sucrose solution of each of

the following concentrations:

0.2 mol dm–3

0.4 mol dm–3

0.6 mol dm–3

0.8 mol dm–3

1.0 mol dm–3

Complete Table 1 to show the volumes of 1.0 mol dm–3 sucrose solution and water that you used to make up each concentration.

3. Stand the boiling tubes containing the sucrose solutions in a water bath set at 30 °C. Use a thermometer to check the temperatures in all tubes reaches 30 °C.

4. Using the core borer, cut six cores from your potato tuber. Make sure you remove any peel on the potatoes. Use a ruler, scalpel and tile to cut all of the cores to the same length. Blot the potato cores dry with a paper towel, i.e. roll each core until it no longer wets the paper towel and dab each end until dry. Do not squeeze the cores. Put each potato core onto a clean square of paper towel which you have numbered in the same way as the boiling tubes.

5. Weigh each potato core. Record these initial masses in a suitable table.6. At the water bath, set the stop clock to zero. Quickly transfer each potato core from its

square of paper towel to its own boiling tube with the same number.7. After precisely 20 minutes, remove the cores from the boiling tubes. Blot the cores dry, as

before. Then reweigh them. Record these final masses in your table.8. Calculate the change in mass and then calculate the percentage change in mass.9. Plot a graph of your processed data and use this to determine the concentration of sucrose

which is which has the same water potential as the potato tuber cells.

Table 1

Concentration of sucrose solution / mol dm–3

0 0.2 0.4 0.6 0.8 1.0

Volume of1.0 mol dm–3 sucrose solution / cm3

0 20

Volume of water / cm3

20 0

EXT. Tradescantia is a house plant. There are small hairs on its flowers. These hairs are made of cells. Figure 1 shows the appearance of cells from one of these hairs after 20 minutes in distilled water. Figure 2 shows cells from another hair after 20 minutes in a solution of potassium nitrate.

(a) What does Figure 2 suggest about the permeability of the plasma membranes

surrounding these cells?

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(b) What is present in the space labelled F? Explain your answer.

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(2 marks)

(c) How would the water potential of the sap in the vacuole of cell E differ from the water

potential of the sap in the vacuole of cell D? Explain your answer.

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Investigation into the effect of a named variable on the permeability of cell-surface

membranes.

The effect of alcohol concentration on the leakage of pigment from beetroot cells

Introduction

Beetroot contains high concentrations of betalin. This is a purple pigment found inside the vacuoles of the cells. The pigment cannot move across undamaged plasma membranes. You will investigate the effect of alcohol concentration on the amount of pigment leaking through beetroot plasma membranes.

In Part 1 of the investigation, you will produce a set of standards. In Part 2 you will use these standards to compare the colour of the solutions obtained when beetroot discs have been soaked in different concentrations of alcohol.

Method

You are provided with:

stock solution of beetroot extract five concentrations of alcohol labelled 100%, 80%, 60%, 40%, 20% discs cut from a beetroot and rinsed thoroughly in water graduated pipettes or syringes test tubes bungs to fit some of the test tubes thermometer large beaker to use as a water bath stopwatch test-tube rack small beakers permanent marker pen water


Part 1: Making the colour standards

1. Use the extract and water to prepare a series of six test tubes containing 5 cm3 of different concentrations of extract. The concentrations should be equally spaced and cover a range from pure water (0%) to pure extract (100%). These will be your colour standards.

2. Label these standards 0, 2, 4, 6, 8, 10.3. Complete Table 1 to show the concentration of extract in each tube.4. Complete Table 1 to show how you made the colour standards in Part 1 of the investigation.

Table 1

Volume of beetroot extract / cm3

Volume of water / cm3

Concentration of extract / % 0 100

Absorbance reading from colorimeter

Part 2: The Investigation

5. Set up a water bath at 30 °C.6. With a second set of test tubes add 2 cm3 of 100% alcohol to a test tube and put a bung in the

tube.7. Label the tube with the alcohol concentration.8. Repeat steps 5 and 6 with alcohol concentrations of 80%, 60%, 40% and 20%.9. Put the tubes of alcohol in the water bath until temperature of the alcohol reaches 30 °C.10. Blot 10 discs of beetroot with a paper towel to remove excess water.11. Gently put two discs of beetroot in each of the five tubes. Replace the bungs as soon as possible

after doing so.12. Leave the tubes in the water bath for 5 minutes. Shake the tubes gently once every minute. Then

remove the tubes from the water bath.13. Immediately pour each solution into a clean test tube, being careful to label the tubes

appropriately. Throw the beetroot discs away.14. Compare each of your solutions with the colour standards you made in Part 1. Note which

standard has the same colour as each of your solutions. If the colour of the solution falls between two of the values you can use the intermediate number. For example, if the colour value is between 2 and 4, record the colour value 3.

15. Record your results in a suitable table.

EXT. The diagram shows the outer layers of a cell from each of three different organisms. One of

the cells is a prokaryotic cell, one is an animal cell and one is a plant cell.

(a) Which of the three cells, A, B or C, is the prokaryotic cell? Give a reason for your answer.

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................................(1 mark)

(b) Complete the table which shows some of the similarities and differences between the outer layers of these cells. Use a tick if the statement is true or a cross if it is not true.

(2 marks)

(c) Penicillin is a substance which kills bacterial cells by damaging their cell walls. As a result, they burst when they take in water.

(i) The concentration of dissolved substances is higher in the cytoplasm of a bacterial cell than it is in the surrounding solution. Explain why water enters the bacterial cell.

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(ii) Penicillin kills bacterial cells but has no effect on plant cells. Suggest why.

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(d) Explain why a plasma membrane can be seen with an electron microscope but not with an optical microscope.............................................................................................................................................................

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A Level Biology Required Practical No. 5Dissection of animal or plant gas exchange or mass transport system or of organ within such a system

Heart Dissection


a sheep’s heart dissecting tray and board dissecting instruments labels and pins.


1. Before you cut the heart examine its external features.

Identify the coronary arteries. Run water into the top of the heart and see if you can see the valves in the aorta and

pulmonary arteries close. Squeeze the heart gently and these valves should open and the water will come out.

2. Cut down each side of the heart to open up the left atrium and left ventricle and the right atrium and right ventricle.

Look for the chordae tendineae attached to the atrio-ventricular valves, and lift the weight of the heart by holding one of these cords over a dissecting needle.

Look how thin the atrio-ventricular valves are. Examine the thickness of the walls of the ventricles. Which side is thicker, and why? Look at the walls of the atria, they are much thinner, can you think why? Push the handle of the dissecting needle up behind the atrio-ventricular valves. You should

notice that the aorta and pulmonary arteries cross over. Describe the difference in vein and arterial tissue. Cut up through the cardiac arteries – can you spot the semi-lunar valves at the base of each

artery? Can you identify the coronary artery at the base of the aorta?

3. Make some little flags from pins and sticky labels and label the parts of the heart that you can identify. Make sure they are legible and visible as you look down on your dissection. Draw and label the heart.

Ask your teacher to check your labelling and take a photograph so you can include it in your notes.

Packing away:

Remove all pins and discard labels. Place pins and dissecting instruments in the beaker with disinfectant. Place the heart in the yellow disposal bag on the trolley.

Use the disinfectant spray to clean the dissecting board and bench, using paper towels to dry them. Dispose of the towels in the disposal bag provided along with your plastic gloves.

EXT. The diagram shows a human heart seen from the front.

(a) (i) Which one or more of vessels A to D contains oxygenated blood?

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(ii) During a cardiac cycle, the pressure of blood in vessel C is higher than the pressure of blood in vessel B. Explain what causes this difference in pressure.

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(b) What does the diagram suggest about the pressure in the atria compared to the pressure in the ventricles at the stage in the cardiac cycle shown?Explain your answer.

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(c) The wave of electrical activity which coordinates the heart beat is delayed slightly at part X. It then passes along part Y to the base of the ventricles.Explain the importance of(i) the slight delay at part X

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(ii) the electrical activity being passed to the base of the ventricles.

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(2 marks)


Use of aseptic techniques to investigate the effect of antimicrobial substances on microbial growth

Aseptic technique producing bacterial plates and use of mast ring of antibiotics

Method


McCartney bottle containing Bacillus sp. bacteria Bunsen burner a beaker containing disinfectant disinfectant spray a prepared agar plate paper towels a chinagraph pencil or other marker a sterile disposable plastic spreader autoclave tape ethanol sterile 1 cm3 pipette and filler forceps Multodisk antibiotic ring.


1. Spray the bench with the disinfectant and wipe down with paper towels. Place the sterile plastic sheet on the cleaned bench.

2. Place the Bunsen burner on a heat proof mat and light it.3. Place the agar plate, the McCartney bottle and the spreader next to the Bunsen burner.4. Write your name, the date and the name of the bacteria on the underside of the agar plate.5. Wash your hands.6. Remove a sterile 1 cm3 pipette from the foil and place the filler onto it.7. Flame the neck of the McCartney bottle.8. Dip the pipette into the bottle and remove 0.3 cm3 of the bacterial culture.

9. Flame the neck of the bottle again and replace the lid.10. Lift the lid of the agar plate at an angle facing the Bunsen burner with your left hand. With your

right hand, squeeze the contents of the pipette onto the surface of the agar.11. Replace the lid of the agar plate and place the pipette into the beaker of disinfectant.12. Take the sterile plastic spreader in your right hand. Facing the Bunsen, lift the lid of the agar

plate and use the spreader to make sure that the bacteria are evenly spread around the surface of the agar.

13. Replace the lid of the plate place the spreader into the beaker of disinfectant.

The disks you will be using have eight arms, each arm containing a different anti-bacterial agent. These are coded as follows:

Code Anti-bacterial agent Code Anti-bacterial agentSTR Streptomycin CHL ChloramphenicolSFZ Sulphafurazole ERY ErythromycinTET Tetracycline CXT CefoxitinAMP Ampicillin PEN Penicillin

Placing the antibiotic ring

1. Take a pair of forceps. Only handle the Multodisk with the forceps.2. Remove a Multodisk from its tin and transfer it to the centre of the agar plate.

Do not hold the disk by one of its arms.3. Carefully flatten the Multodisk onto the surface of the plate, using the forceps.

Place the forceps into the beaker of disinfectant.4. Hold the lid of the plate in place with two pieces of tape.5. Place your plate upside down in an incubator at 25 °C for 48 hours.6. Now wash your hands.

After incubation, Caution - plates must not be opened after they have been incubated

7. Examine your plate and try to identify the colonies which have not been able to grow near the Multodisk arm(s). These are called zone(s) of inhibition. Turning the plate upside down and using a ruler measure the diameter of the zones of inhibition. Calculate the area of the zone of inhibition using the formula

Area of zone = πr2 (Use 3.14 as π)

Record your results in a suitable table.

EXT. 1. Hospitals can check to see if a strain of bacteria causing an infection is resistant to a range of antibiotics by using a multodisc. A multodisc contains different antibiotics.

• The bacteria are isolated from a patient.• The bacteria are spread on nutrient agar in a Petri dish.• The multodisc is placed on the agar.

The figure below shows a Petri dish with the bacteria, in which is placed a multodisc containing six different antibiotics.

1

2

3

4

5

6

m ultod isc

bacteria presen t

cleararea

Petr i d ishw ith nutrientagar

Key:1 te tracycline

2 am oxicillin

3 neom ycin

4 streptom ycin

5 penic illin

6 su lfonam ide

(i) Explain why there are clear areas of agar in the Petri dish.

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(ii) Using the figure above, name the antibiotic that is most effective against the bacteria causing the infection.

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(iii) Suggest three reasons why a hospital might use a multodisc to select the most suitable antibiotic for treating a patient.

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[Total 5 marks]

EXT. 2. Drugs, such as antibiotics, are often first discovered in the natural environment.

Explain why it may become increasingly difficult to discover new drugs in the future.

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Use of chromatography to investigate the pigments isolated from leaves of different plants e.g. leaves from shade-tolerant and shade intolerant plants or leaves of different colours

An Investigation of pigments present in

leaves Introduction

In plants, chlorophyll is the main pigment that absorbs light energy during photosynthesis. Most plants have other photosynthetic pigments as well and these are not green. You will be using a technique called chromatography to separate chlorophyll and other pigments from two different leaves, A and B.

Method


boiling-tube rack two boiling tubes with bungs small glass measuring cylinder solvent chromatography paper glass rod two leaves, A and B core borer white tile ruler pencil drawing pins marker pen sticky tape

Safety

Wear eye protection and work in a well-ventilated room or fume cupboard.


1. Set up two boiling tubes at the start of the investigation. Add 3 cm3 of solvent to each of the twoboiling tubes. Put a bung in the top of each tube and stand them upright in a rack. Label the tubes A and B.

2. Take a piece of chromatography paper that fits into the boiling tube, as shown in the diagram. Rule a pencil line 2 cm from the bottom of the filter paper. This line is called the origin. Write leaf A at the top of the chromatography paper in pencil.

3. Cut a disc from leaf A with a cork borer. Try to avoid the veins and midrib of the leaf when you do this.

4. Place the leaf disc on the chromatography paper at the centre of the line marking the origin. Crush the disc into the paper with the end of a glass rod. The crushed leaf disc should leave a stain on the chromatography paper.

5. Pin the chromatography paper to the bung with a drawing pin, and then put the chromatography paper into the tube labelled A as shown in Figure 1. Make sure the end of the chromatography paper is in the solvent and that the solvent does not come above the origin. Put the tube carefully back into the rack and do not move it again.

Figure 1

6. Let the solvent run up the chromatography paper until it almost reaches the top of the paper. Remove the chromatography paper from the tube and immediately draw a pencil line to show how far the solvent moved up the paper. This line marks the solvent front.

7. Replace the bung in the tube.8. The filter paper with its coloured spots is called a chromatogram. Let the

chromatogram dry. Using a pencil, draw round each coloured spot on the chromatogram.

9. Repeat step 2 with the second piece of paper but write B at the top of the chromatography paper.10. Repeat steps 3–8 with leaf B.

Calculate the Rf value for each of the pigment spots on each chromatogram.

Rf value = Distance moved by pigment from origin to centre of pigment spot Distance from origin to solvent front

EXT. Red seaweeds are algae which contain, in addition to chlorophyll, a red pigment called phycoerythrin. Green seaweeds do not contain phycoerythrin. Both phycoerythrin and chlorophyll absorb light energy which can be used in photosynthesis. The graphs show the percentage of light of different wavelengths absorbed by sea water, by chlorophyll and by phycoerythrin.

Use information from the graphs to explain why red seaweeds are usually found in deeper water (further down the shore) than green seaweeds.

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Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts

The effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP

In this investigation you will use a chloroplast suspension and a blue dye called DCPIP to monitor the rate of dehydrogenase activity. DCPIP goes from blue to colourless when it accepts electrons released by the chlorophyll.

Method


spinach leaves access to a blender measuring cylinder muslin (or material for filtering) filter funnel 3 beakers ice isolation medium (cold) DCPIP solution (cold) distilled water (cold) ammonium hydroxide solution (cold) test tubes test-tube rack syringes (1cm3 and 5 cm3 ) piece of aluminium foil lamp marker pen timer


1. Put about 50 cm3 of isolation medium into a beaker.2. Tear 8 spinach leaves into small pieces and put the pieces into the isolation

medium in the beaker. Do not put pieces of the midrib or the leaf stalk into the beaker.

3. Half fill a large beaker with ice and place a small beaker on top of the ice.4. Put 3 layers of muslin over the top of the filter funnel and wet it with the isolation

medium. Rest the filter funnel in the small beaker on the ice.5. Pour the spinach and isolation medium into the blender and blend for about 15 seconds.

Pour the blended mixture back into the beaker.

6. Pour a little of your blended mixture through the muslin in the filter funnel. Carefully fold and squeeze the muslin to assist the filtering process. Repeat until most of the blended mixture has been filtered. Label this filtrate which is in the small beaker on ice as ‘chloroplast suspension’.

7. Label five test tubes A, B, C, X and Y. Stand these five tubes in the ice in the large beaker. Position the lamp about 10 cm from the beaker so that all tubes are illuminated. Turn on the lamp.

8. Set up tubes A and B as follows:Tube A

Put 5 cm3 DCPIP solution + 1 cm3 water + 1 cm3 chloroplast suspension in the tube. Immediately wrap the tube completely in aluminium foil to exclude light.

Tube B

Put 5 cm3 DCPIP solution + 1 cm3 water + 1 cm3 isolation medium in the tube.

Tubes A and B are control experiments. Leave both tubes until the end of your investigation.

9. Set up tube C as follows:Tube C

Put 6 cm3 water + 1 cm3 chloroplast suspension in the tube.

Tube C is for you to use as a standard to help you to determine when any colour change is complete.

10. Set up tube X as follows:Tube X

Put 5 cm3 DCPIP solution + 1 cm3 water in the tube.

Add 1 cm3 chloroplast suspension to tube X, quickly mix the contents and start the timer. Record in seconds how long it takes for the contents of tube X to change colour from blue-green to green. This is when all signs of blue have disappeared. Use tube C to help you determine when the colour change is complete.

11. Repeat step 10 four more times.12. Set up tube Y as follows:

Tube Y

Put 5 cm3 DCPIP solution + 1 cm3 ammonium hydroxide in the tube.

Add 1 cm3 chloroplast suspension to tube Y, quickly mix the contents and start the timer. Record in seconds how long it takes for the contents of tube Y to change colour from blue-green to green. This is when all signs of blue have disappeared. Use tube C to help you determine when the colour change is complete. However if this has not taken place within 300 seconds (5 minutes), record the colour at this point.

13. Repeat step 12 four more times.14. Record your data in a suitable table.

At the end of your investigation, record the colour of the mixtures in tubes A and B.

EXT. (a) The diagram shows part of the light-independent reaction of photosynthesis.

(i) How many carbon atoms are there in one molecule of glycerate 3-phosphate?

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.......................(1 mark)

(ii) What is the function of each of the following in the reactions shown in the diagram?

Reduced NADP ...........................................................................................................................

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ATP ..............................................................................................................................................

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(b) Radioactive carbon dioxide was supplied to a culture of photosynthesising single-celledalgae. At 5-second intervals, samples of the culture were dropped into boiling alcohol to stop all chemical reactions. The radioactive substances identified in these samples are given in the table.

Explain how information in the table provides evidence for the following.

(i) Glycerate 3-phosphate is converted into triose phosphate.

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.........................(1 mark)

(ii) The reactions given in part (a) form part of a cycle of reactions.

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Investigation into the effect of a named variable on the rate of respiration of cultures.

An investigation of the effect of temperature on respiration in yeast.

Yeast is a single-celled fungus. It can respire aerobically and anaerobically. During aerobic respiration, the transport of electrons is linked to the synthesis of ATP. In this investigation these electrons will be accepted by a substance called methylene blue. When methylene blue accepts electrons, it changes from blue to colourless.

Method


yeast and glucose mixture methylene blue test tubes test-tube rack beaker to act as water bath a way of changing the temperature of the water bath graduated pipettes or syringes

marker pen thermometer timer

You should read these instructions carefully before you start your investigation.

1. Use the beaker to set up a water bath at 35 °C.2. Label five test tubes 1 to 5.3. Shake the yeast and glucose mixture.4. Add 2 cm3 of the yeast and glucose mixture to all five tubes.5. Place all five tubes in the water bath and leave them until the contents reach 35 °C.

Make sure the water bath stays at 35 °C6. Add 2 cm3 methylene blue to test tube 1.7. Immediately shake this tube for 10 seconds and replace the tube in the water bath.

Note the time and do not shake this tube again.8. Record how long it takes for the blue colour to disappear in the tube.9. Repeat steps 6 to 8 for the other four tubes.10. Your teacher will tell you which other temperatures to use. Repeat steps 1 to 9 at

each temperature.

EXT. The diagram gives an outline of the process of aerobic respiration.

(a)(i) Complete the table by naming stages A and B and giving the location of each stage in a cell such as a liver cell.

(2 marks)

(ii) How many carbon atoms are there in each pyruvate ion? .............................................................

(1 mark)

(iii) What happens to the H+ ions and electrons released in stage C?

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(b)In aerobic conditions, ATP is produced by substrate-level phosphorylation and by oxidative phosphorylation. Use information in the diagram to find the net yield of molecules of ATP per molecule of glucose by

(i) substrate-level phosphorylation; ..............................................................................

(ii) oxidative phosphorylation. .......................................................................................

(2 marks)

(c) (i) One mole of glucose releases 2880 kJ of energy when burned completely in oxygen. Hydrolysis of one mole of ATP to ADP and phosphate releases 31 kJ of energy. Use your answers from part (b) to calculate the percentage efficiency of energy transfer from glucose to ATP by aerobic respiration. Show your working.

Percentage efficiency = ........................................%(2 marks)

(iii) What happens to the energy which is not transferred to ATP?

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(iv) Explain why ATP is better than glucose as an immediate energy source for cell metabolism.

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(v) Give three uses of energy from ATP in a liver cell.

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(3 marks)


Investigation into the effect of an environmental variable on the movement of an animal using either a choice chamber or a maze

Using choice chambers to investigate responses in invertebrates to light/dark and humid/dry conditions

Method


a choice chamber with nylon mesh fabric silica gel humidity test strips (cobalt chloride strips which have been dried – blue when dry and pink

when moist) paper towels water black paper sticky tape maggots (or woodlice) beaker teaspoon forceps

Control experiment

1. Set up the choice chamber with nothing in the base quarters.2. Place 12 maggots in the chamber through the central hole, using the teaspoon.3. Wait 4 minutes then record the number of maggots in the left and right halves

of the choice chamber. Record your results.

If the left and right halves have no effect on the distribution of the maggots the expected results would be six in each half, but this will not always occur because of chance distribution. If your results are not 6 in each half do a statistical test on your results to discover the probability of them occurring by chance. If this test shows a greater than 5% probability of the results occurring by chance then you can proceed with the experiment.

The effect of light

1. Cover half the choice chamber with black paper to make it dark.

2. Place 12 maggots in the chamber through the central hole, using the teaspoon.3. Wait 4 minutes and then record the number of maggots in the dark and the light halves.

If light has no effect on the distribution of maggots the expected results would be six in each half. Now do a statistical test on your results to find the probability of them occurring by chance.

The effect of humidity

1. Place damp paper towel in one half of the choice chamber and silica gel in the other. Use the humidity test strips to ensure that a humidity gradient exists in the chamber before adding the maggots. Use the forceps to place the humidity test strip.

2. Place 12 maggots in the chamber through the central hole.3. Wait 4 minutes and then record the number of maggots in the humid and the dry halves.

The effect of light and humidity

In reality living organisms do not have simple choices between one pair of contrasting environmental factors. If you have time do a final experiment with the choice between dark and dry, dark and humid, light and dry, light and humid. Again test the probability of your results occurring by chance with a statistical test.

EXT. IAA is a substance that affects the growth of plants. It is produced in the tips of shoots and moves downwards in the stem to the rest of the plant. A series of experiments was performed to investigate the effect of the IAA on the growth of cucumber seedlings.

(a) Figure 1 shows the results of an investigation into the effect of unidirectional light on IAA.

Figure 1

A g a r b lo c k

L ig h t L ig h t

S h o o t tip

2 5 .5 2 4 .8

1 7 .2 2 5 .2

Im p e rm ea b leg lass b arr ie r

Im p e rm e ab leg la ss b a rr ie r7 .8

Im p e rm ea b leg lass b arr ie r

T ip s an d k ep tin to ta l d a rk n e ss

A B

A B

C D

(i) Give one reason for the use of the impermeable glass barriers.

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(1)

(ii) What do the results of this experiment show about the effect of unilateral light on IAA? Use evidence from Figure 1 to support your answer.

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(3)

(b) Figure 2 shows the ways in which two groups of cucumber seedlings were cut before being used in a second investigation

Figure 2

The two types of cut seedlings, P and Q, were grown in different growth media over a four-hour period. The table shows the results.

Group of cut Growth medium

Mean increase in length/mm

seedlings used

Grown in the dark

Grown in blue light

P 1% sucrose solution 1.2 0.8P Solution of 1% sucrose and 6 mg dm–3 IAA 3.9 5.2Q 1% sucrose solution 4.1 3.3Q Solution of 1% sucrose and 6 mg dm–3 IAA 4.9 5.7

(i) The cut seedlings were grown in sucrose solution, rather than in distilled water.Give one reason why.

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(ii) When they were both grown in the dark, the two groups of seedlings responded differently to the inclusion of IAA in their growth media. Suggest one explanation for this different response.

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(iii) Describe the effect of blue light on the growth of seedlings P and Q.

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(c) Many fungi are parasites on plants. Uptake of IAA from the host plant affects the ability of these parasitic fungi to invade their plant host.

The uptake of IAA by a particular fungus was investigated. Two phenotypes of the fungus were used, the wild type and a particular mutant.

The bar chart shows the effect of DNP on the uptake of IAA by this fungus. DNP is a drug that affects the gradient of hydrogen ions across mitochondrial membranes.

M e anup ta k eo f IA Abyfu n g u s /a rb itra ryun its

2 5

2 0

1 5

1 0

5

0H ea t-k ille dw ild ty p e

W ild ty pe M u tan te

K ey : U n tre a ted Trea te d w ith D N P S tan d ard d e v ia tio n o fm ea n

Using evidence from the information given above and your own knowledge,

(i) explain how IAA is taken up by the cells of this fungus

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(ii) suggest how the mutation affected the cells of this fungus.

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(Total 15 marks)


Production of a dilution series of a glucose solution and use of colorimetric techniques to produce a calibration curve with which to identify the concentration of glucose in an unknown ‘urine’ sample

Sugar in the urine is one of the first indications of diabetes.

Method


10 mmol dm–3 glucose standard. distilled water urine samples from Tom, Dick and Harry Benedict’s solution graduated pipettes (2 and 1 cm3) and pipette filler test tubes test-tube rack water bath set at 90 °C colorimeter and cuvettes

Prepare urine samples for testing

1. Label the test tubes with the name of the patient and add 2 cm3 urine samples from each patient.2. To each test tube add 2 cm3 Benedict’s solution. Mix the contents of the tube.

Prepare the glucose calibration curve

1. Label six test tubes 0 to 10 mmol dm–3 as shown in the table below.2. Dilute the glucose standard (10 mmol dm–3) with water in the labelled test tubes and complete the

table to show volumes used to achieve each concentration.

Concentration of final solution/ mmol dm–3

0.0 2.0 4.0 6.0 8.0 10.0

Amount of water / cm3 2.0Amount of glucose standard / cm3 0.0

3. Add 2 cm3 of Benedict's solution to each tube. Mix the contents of each tube.4. Place all the test tubes into the water bath together (including the tubes with the urine samples)

and time for four minutes. Allow to cool before taking readings from the colorimeter.5. Use the contents of the 0.0 mmol dm–3 glucose solution tube, which you have heated with Benedict's, as a blank to calibrate the colorimeter to zero absorbance. Place the remaining

samples in cuvettes into the colorimeter and read the absorbance.

6. Record your results in a table and plot a graph of the absorbance of the known concentrations of glucose.

7. Using the graph and the absorbance values obtained for the urine samples read off from the graph the concentration of glucose in the urine samples.

Record your results in a suitable table.

EXT. Lactose is present in milk. It is broken down by lactase into glucose and galactose. This is shown in the equation.

lactose + water glucose + galactose

(a) Name the type of reaction shown in the equation.

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(c) The molecular formula of galactose is C6H12O6. What is the molecular formula of lactose?

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(c) Doctors use a lactose tolerance test to find out if a person is lactose intolerant. In this test, the person is given a solution of lactose to drink. Blood glucose concentration is then measured over the next two hours.A lactose tolerance test was carried out on a healthy man who was lactose tolerant, and on a man who was lactose intolerant. The results for the first hour are shown in the table.

(i) The blood glucose concentration changed in the healthy man after he had taken the test. Describe how.

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(2 marks)

(iii) Explain the results for the lactose intolerant man.

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Investigation into the effect of a named environmental factor on the distribution of a given species

Investigation into distribution of plant species along Darland Banks (heathland) in response to (a variety of) abiotic factors using a line transect.

Method


quadrat (1m x 1m) tape measure multi-function environment meter anemometer thermometer and borer (to make hole for thermometer) two test tubes per interval spatula universal indicator


1. Before going to the heathland, looking at Google maps, decide on your area of investigation.2. Go to the heathland and set up your line transect. Make sure you can identify all plant

species to be counted by the shape of its leaves.3. Lay out the quadrats at right angles to the line transect at 2m intervals.4. Use the quadrats to calculate percentage cover of the plant species. Repeat this at

each interval.5. Using the multi sensor, take a light reading, humidity reading, and temperature

reading. Repeat this for each interval.6. Using the anemometer, take a wind speed reading at the interval. Repeat this for

each interval.7. Take a soil sample and dilute with distilled water in a test tube. Leave to settle for 5

minutes and remove top 1ml with pipette and add to separate test tube. Add two drops of universal indicator and record colour/ph. Repeat this at each interval.

8. Record the % cover of each plant species and the sensor readings at each interval in a table.

9. Produce a kite diagram of the species distribution in response to one or more abiotic factor.

EXT. The community present in a roadside ecosystem was investigated.

(a)Explain what is meant by:

(i) community; ...........................................................................................................................

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(ii) ecosystem. ............................................................................................................................

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(b)The diagram shows a section through a road which has a sloping bank and hedge on each side.

The following plant species were found growing on 10-metre lengths of the north-facing and south-facing road banks.

(i) Use the formula:

to calculate the index of diversity for the plants growing on the north-facing road bank. Show your working.

Index of diversity = ...............................

(2 marks)(ii) Give one advantage of calculating the index of diversity rather than just

recording the number of species present.

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(iii) Suggest and explain how one abiotic factor might have caused differences in plant growth on the two road banks.

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(iv) Explain why the south-facing road bank is likely to show greater ecological stability than the north-facing road bank.

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(v) The south-facing road bank would also be expected to have a higher diversity of animals. Suggest one reason for this.

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(c) In order to estimate the population of woodlice living on the north-facing road bank, four pitfall traps were set in the ground at 2-metre intervals and left for 24 hours. All the woodlice that had fallen into the traps were marked on their underside with quickdrying paint and released back into their habitat. The next day the traps were examined again and the numbers of marked and unmarked woodlice were counted. The results are shown in the table.

(i) Use the data to estimate the woodlouse population in this area. Show your working.

Population = ..........................................

(2 marks)

(ii) Suggest two reasons why it is not possible to make a reliable estimate of the woodlouse population size from these data.

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Command Words

qclscience.weebly.com · web viewapparatus and techniques at a use appropriate apparatus to record...

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